Add to_regnamespace() and to_regrole() to the documentation.

Commits cb9fa802b3 and 0c90f6769d added these functions,
but did not bother with documentation.

doc/src/sgml/func.sgml

@@ -15819,6 +15819,14 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
     <primary>to_regtype</primary>
    </indexterm>
 
+   <indexterm>
+    <primary>to_regnamespace</primary>
+   </indexterm>
+
+   <indexterm>
+    <primary>to_regrole</primary>
+   </indexterm>
+
   <para>
    <xref linkend="functions-info-catalog-table"> lists functions that
    extract information from the system catalogs.
@@ -16009,6 +16017,16 @@ SELECT pg_type_is_visible('myschema.widget'::regtype);
        <entry><type>regtype</type></entry>
        <entry>get the OID of the named type</entry>
       </row>
+      <row>
+       <entry><literal><function>to_regnamespace(<parameter>schema_name</parameter>)</function></literal></entry>
+       <entry><type>regnamespace</type></entry>
+       <entry>get the OID of the named schema</entry>
+      </row>
+      <row>
+       <entry><literal><function>to_regrole(<parameter>role_name</parameter>)</function></literal></entry>
+       <entry><type>regrole</type></entry>
+       <entry>get the OID of the named role</entry>
+      </row>
      </tbody>
     </tgroup>
    </table>
@@ -16152,10 +16170,13 @@ SELECT collation for ('foo' COLLATE "de_DE");
   <para>
    The <function>to_regclass</function>, <function>to_regproc</function>,
    <function>to_regprocedure</function>, <function>to_regoper</function>,
-   <function>to_regoperator</function>, and <function>to_regtype</function>
-   functions translate relation, function, operator, and type names to objects
-   of type <type>regclass</>, <type>regproc</>, <type>regprocedure</type>,
-   <type>regoper</>, <type>regoperator</type>, and <type>regtype</>,
+   <function>to_regoperator</function>, <function>to_regtype</function>,
+   <function>to_regnamespace</function>, and <function>to_regrole</function>
+   functions translate relation, function, operator, type, schema, and role
+   names to objects of
+   type <type>regclass</>, <type>regproc</>, <type>regprocedure</type>,
+   <type>regoper</>, <type>regoperator</type>, <type>regtype</>,
+   <type>regnamespace</>, and <type>regrole</>
    respectively.  These functions differ from a cast from
    text in that they don't accept a numeric OID, and that they return null
    rather than throwing an error if the name is not found (or, for